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Am J Physiol Cell Physiol 256: C772-C778, 1989;
0363-6143/89 $5.00
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AJP - Cell Physiology, Vol 256, Issue 4 C772-C778, Copyright © 1989 by American Physiological Society

ARTICLES

Activation of a Cl-dependent K flux by cAMP in pig red cells

H. D. Kim, S. Sergeant, L. R. Forte, D. H. Sohn and J. H. Im
Department of Pharmacology, School of Medicine, University of Missouri-Columbia 65212.

Activation of a Cl-dependent K flux by adenosine 3',5'-cyclic monophosphate (cAMP) was characterized in pig red cells, a cell type that lacks both the Ca-activated K channel and the Na-K-Cl cotransport pathway. As in other red cells, both Cl-dependent K efflux and K influx are stimulated on cell swelling. Although pig red cells fail to respond to beta-adrenergic stimuli, it is possible to raise the intracellular cAMP content by preincubating cells in the presence of 1 mM cAMP. The Cl-dependent K flux was compared in cells having a basal cAMP content of approximately 0.29 nmol/g hemoglobin vs. cAMP-loaded cells having approximately 8.4 nmol cAMP/g hemoglobin. Loading with cAMP stimulated both Cl-dependent K efflux and influx of hypotonically swollen cells. In maximally swollen cells whose volume was increased by approximately 17%, the Cl-dependent Rb influx occurs with a maximum velocity (Vmax) of 17.9 +/- 3.2 mumol.g hemoglobin (Hb)-1.h-1 and Km for Rb of 22.9 +/- 4.1 mM. In cAMP-loaded cells, both Vmax and Km were increased to 59.8 +/- 8.5 mumol.g Hb-1.h-1 and 63.1 +/- 8.8 mM, respectively. The Cl-dependent Rb influx is much larger in young cells than in old cells. However, both cell types respond to cAMP activation. Whereas cAMP and its analogues, 8-bromoadenosine 3',5'-cyclic monophosphate and dibutyryl adenosine 3',5'-cyclic monophosphate are stimulatory, AMP and guanosine 3',5'-cyclic monophosphate (cGMP) are not. These findings suggest that, like other ion transport systems, the Cl-dependent K flux of pig red cells is endowed with the capacity to respond to cAMP.


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[Abstract] [Full Text] [PDF]


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